Exemplary embodiments of the present invention relate to a semiconductor device, and more particularly, to a fuse circuit of a semiconductor device.
In typical memory devices, a large number of memory cells are integrated into a single chip. When a defect occurs in any one of the memory cells, an entire memory chip is discarded as a defective product. The current trend is to integrate a larger number of memory cells into a chip having a limited size in order to increase the integration density of memory devices. This goal is frustrated, if an entire memory chip is discarded as a defective product even when a defect occurs in any one of memory cells. In this case, the number of memory chips to be discarded as defective products will increase causing inefficient production of semiconductor memory devices.
To solve these limitations, a typical semiconductor memory device is provided with a redundant cell, as well as, a fuse circuit. The fuse circuit includes a plurality of fuses, and a defective cell is replaced with a redundant cell according to a blowing of a fuse in a repair process. A redundant cell and a fuse circuit are formed in a spare space during a semiconductor fabrication process. A repair process is performed to replace a defective memory cell with a redundant cell.
Fuses are classified into physical fuses and electrical fuses. A method using physical fuses performs a repair process to selectively cut fuses by irradiating a laser beam onto the fuses at a wafer level where a semiconductor process is completed. The disadvantage of the physical fuses is that the repair process can be performed only at the wafer level, that is, before the semiconductor memory device is fabricated in a package.
To address this disadvantage, electrical fuses are used. Fuses which are programmable at a package level are generally referred to as electrical fuses. The electrical fuses may be programmed by electrically changing the fuse connection state. The electrical fuses may be classified into anti-type fuses, which change from an open state to a short state, and blowing-type fuses, which change from a short state to an open state.
The electrical fuses are preferred over physical fuses with respect to yield management because they can be programmed after packaging. However, since the electrical fuses are processed at the package level, it is impossible to confirm the connection states of the programmed fuses with naked eyes, as opposed to the physical fuses which are processed at the wafer level. In order to confirm the connection states of the electrical fuses, the package must be removed. However, if the finished package is removed for testing purposes, the value of the finished product is degraded and the efficacy of the test is lowered.